Lighting unit for motor vehicles

ABSTRACT

A lighting unit for vehicles has a plurality of semiconductor light sources distributed in a grid. The grid of semiconductor light sources is divided into at least two grid segments, the grid segments being each activatable independently of each other and/or assigned to a different light functions, with an optical element in the beam path of a light beam emitted by the semiconductor light sources. The semiconductor light sources ( 3 ) are arranged on a common carrier substrate ( 5 ), with a chip cover ( 6 ) transparent to light in the direction of light propagation, in that the chip cover ( 6 ) is filled with a light-scattering and/or light-converting auxiliary material ( 8 ) and in that a shading device ( 9 ) is provided such that, in the boundary region between the activated grid segment ( 10 ) and the unactivated grid segment ( 11 ), a relatively steep transition of light intensity is adjustable to form a light/dark boundary.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application of InternationalApplication No. WO 2004/088202 PCT/EP2004/003566 filed on Apr. 3, 2004and claims priority to German Application No. 103 15 133.8 filed on Apr.3, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a lighting unit for vehicles with a plurality ofsemiconductor light sources distributed in a grid, the grid ofsemiconductor light sources being divided into at least two gridsegments, the grid segments being each activatable independently of eachother and/or assigned to a different light function, with an opticalelement in the beam path of a light beam emitted by the semiconductorlight sources

2. Related Art

From DE 100 09 782 A1 is known a lighting unit for motor vehicles, whichhas as a light source a plurality of semiconductor light sourcesarranged in a grid. The grid of semiconductor light sources is dividedinto grid segments, wherein each differently activatable grid segmentcan be assigned a different light function. The light beam emitted bythe grid segments is projected according to a predetermined lightdistribution by means of a lens mounted in front in the direction oflight propagation. Between the grid of semiconductor light sources andthe lens is arranged a stop, so that the known lighting unit works onthe basis of the projection principle.

A disadvantage of the known lighting unit is that the grids or gridsegments have a relatively large two-dimensional extent, as eachsemiconductor light source has its own housing. Furthermore, it isalways necessary for a stop to be arranged between the grid ofsemiconductor light sources and the lens.

SUMMARY OF THE INVENTION

It is the object of the present invention to develop a lighting unit formotor vehicles in such a way that the lighting unit has a more compactand space-saving construction.

To achieve this object, the invention is a lighing unit for vehicleswith a plurality of semiconductor light sources distributed in a grid,the grid of semiconductor light sources being divided into at least twogrid segments, the grid segments being each activatable independently ofeach other and/or assigned to a different light function, with anoptical element in the beam path of a light beam emitted by thesemiconductor light sources where the semiconductor light sourcesarranged on a common carrier substrate, with a chip cover transparent tolight in the direction of light propagation, in that the chip cover isfilled with a light-scattering and/or light-converting auxiliarymaterial and in that a shading device is provided such that, in theboundary region between the activated grid segment and the un activatedgrid segment, a relatively steep transition of light intensity isadjustable to form a light/dark boundary.

The particular advantage of the invention lies in that, due to theconcentrated arrangement of the semiconductor light sources on a commoncarrier substrate and the associated high packing density ofsemiconductor light sources, the luminance of the light source can besubstantially increased. For ease of manufacture, the individualsemiconductor light sources can be arranged as chips on a common carriersubstrate. A common chip cover which is transparent to light and alight-scattering and/or light-converting auxiliary medium integratedtherein cause a homogeneously illuminating light exit surface. Aspatially concentrated light source with a relatively high luminance isadvantageous according to the invention. A shading device causes arelatively steep transition of light intensity in the boundary regionbetween a first grid segment activated by a control unit and a secondgrid segment not activated by the control unit. As a result, arelatively sharp light/dark boundary can be achieved. The grid segmentscan, for example, be activated to form a dipped beam and a main beam.

According to a development of the invention, the shading device isdesigned as a partition arranged between the first grid segment and thesecond grid segment, the free end of the partition being spaced apartfrom a front side of the chip cover in such a way that there is a minorlight interaction between the adjacent grid segments. The lightfunctions of the individual grid segments are only slightly disturbed byscattered light of the adjacent grid segment. The design of the shadingdevice as a partition allows unique fixing of mutual light control ofadjacent grid segments already during manufacture of the light source.

Advantageously, the partition projects from the carrier substrate insuch a way that, in case of simultaneous activation of adjacent gridsegments, the formation of a black line on a measuring screen isprevented.

According to a development of the invention, the semiconductor sourcesare respectively designed as chips, the chips being arranged on a commoncarrier substrate. As a result, a plurality of semiconductor sources canbe formed to save space and miniaturise.

According to a development of the invention, optical elements arearranged by adhesion on the front side of the chip cover and adapted tothe corresponding chips. As a result, selective light conductiondirectly at the light exit surface of the light source is made possible.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Two practical examples of the invention are described in more detailbelow with the aid of the drawings. They show:

FIG. 1: a schematic cross-section through a lighting unit,

FIG. 2: a top view of a grid of semiconductor light sources,

FIG. 3: an enlarged cross-section through a lighting unit according to asecond embodiment, and

FIG. 4: an illuminance distribution of the lighting unit projected ontoa measuring screen, in a boundary region between an activated first gridsegment and an un activated second grid segment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

A lighting unit for vehicles, in particular motor vehicles, essentiallyconsists of a light source 1 and an optical element 2 which projects thelight beam emitted from the light source 1 directly according to apredetermined light distribution.

The lighting unit according to the invention can serve, for example, asa headlamp for the generation of a dipped beam, main beam, motorway beamand/or cornering beam function.

The light source 1 is formed from a plurality of semiconductor lightsources 3, in particular LED light sources (light-emitting diodes),which are arranged after the fashion of a grid 4 on a common carriersubstrate 5.

As can be seen from FIG. 2, the semiconductor light sources 3 arearranged regularly adjacent to and under each other. The semiconductorlight sources 3 are designed as so-called chips which are mounted on acommon carrier substrate 5.

As FIG. 1 shows, the chips 3 are provided with a common transparent chipcover 6 on one side facing away from the carrier substrate 5. The chipcover 6 and the carrier substrate 5 form a housing 7 which completelysurrounds the semiconductor light sources 3. The chip cover 6 isdesigned as a planar cast body which is mounted after fitting thecarrier substrate 5 with the chip 3.

The cast body 6 has a light-scattering and/or light-converting auxiliarymaterial 8, in particular a luminescent material. The auxiliary material8 causes white light to be emitted from a front side 15 of the chipcover 6 in the direction of light propagation. The auxiliary material 8is evenly distributed in the cast body 6.

In the embodiment according to FIG. 3, an optical element 16 is designedas a primary optical element (lens) abutting directly on the front side15 of the cast body 6 by adhesion. The primary optical element has aplurality of lens elements 17 which are respectively oriented inrelation to the chip 3. The primary optical element 16 is manufacturedin one piece from a plastic material and joined to the cast body 6 byadhesion on the front side 15 thereof.

The grid 4 of semiconductor light sources 3 is divided by means of ashading device 9 into an upper grid segment 10 and a lower grid segment11. The upper grid segment 10 serves to produce a dipped beam function.The lower grid segment 11 serves to produce a main beam function. It isconnected to the upper grid segment 10 to produce the main beam by meansof a control unit, not shown, so that all semiconductor light sources 3of the grid 4 are in use.

The shading device 9 is designed as a partition which extendsperpendicularly to the extent of the carrier substrate 5 between thelatter and the housing cover 6. The partition 9 causes perfect lightseparation of the two grid segments 10 and 11. The partition causes inparticular, in case of activation of only one grid segment 10 or 11, noedge stripe or a reduced edge stripe to light up as well along thepartition 9 of the other grid segment 11 or 10. Such lighting up couldbe caused by the auxiliary material 8 which is located in the adjacentgrid segment 10 or 11. Advantageously, a sharp light/dark boundary canbe formed as a result.

A free end of the partition 9 is designed to taper as an apex 18 andarranged at a distance from the front side 15 of the cast body 6. Thisensures that, with simultaneous activation of the first and second gridsegments 10 and 11, no disturbing dark stripe is projected by theboundary region thereof. Thus a homogeneous light transition is obtainedin the boundary region between the grid segments 10 and 11 to form themain beam. Furthermore, alternatively a second grid segment can add acornering beam or a motorway beam homogeneously to the dipped beam.

The carrier substrate 5 forms, together with the semiconductor lightsources 3 arranged in a grid, a semiconductor light source array. As aresult, a concentrated and space-saving light source can be produced,which if necessary has grid segments activated differently in a simplemanner. Advantageously, miniaturisation of a light source can beproduced by this means, which in a manner allowing ease of manufactureimproves variability in the use of light functions. Firstly, the arraycan have a predetermined shape which is dependent on the requiredluminosity, light function or the shape of the opening in the vehiclebody. This can be effected by suitably trimming the chip wafer.

Secondly, the chips 3 themselves can also have a shape adapted to therequirements. For instance, the chips 3 can be of triangular orhoneycomb-like structure, so that the break in the 15° light/darkboundary can be simulated better or the packing density is greater.

Due to the extent of the shading device 9, a predetermined light/darkboundary can be produced. Individual groups of semiconductor lightsources 3 can be combined to form basic light, asymmetrical light orother light fractions.

Advantageously, the carrier substrate 5 can also contain the activationcircuit for the semiconductor light sources 3. The control unit can bedesigned as an integrated circuit, for example.

The carrier substrate 5 can be made of an electrically conductivematerial, in particular copper, or a non-conductive material, inparticular ceramic material or a plastic material. The carrier substrate5 serves as a carrier for the light components or passive or activecomponents and for current conduction. The chips 3 are connected by thebond technique to corresponding terminals of the carrier substrate 5 andcompletely covered by the cast surface 6.

For this purpose, electrically conductive strip conductors are arrangedon the carrier substrate 5.

The light source 1 according to the embodiment in FIG. 1 is arranged ina focal plane of the lens 2 (secondary optical element), so that thelight beam emitted by the light source 1, 3 is projected according to apredetermined light distribution exclusively by the shape of the lens 2.

In FIG. 4 is shown the illuminance distribution L over the distance xwhich appears on a measuring screen when only the first grid segment 10is activated to form a dipped beam function. The illuminancedistribution is shown according to the unbroken line, a high gradient ofilluminance distribution being produced in a boundary region G betweenthe first grid segment 10 and the second grid segment 11. This isobtained by the shading device 9 which is arranged in this boundaryregion G. As a result, a sharp light/dark boundary can be obtained.

Compared with this, the illuminance distribution is shown without thepresence of a shading device 9 in the boundary region G (broken line).Due to the continuous and steady transition of this illuminancedistribution from the first grid segment 10 to the second grid segment11, a sharp light/dark boundary can be obtained.

As various modifications could be made to the exemplary embodiments, asdescribed above with reference to the corresponding illustrations,without departing from the scope of the invention, it is intended thatall matter contained in the foregoing description and shown in theaccompanying drawings shall be interpreted as illustrative rather thanlimiting. Thus, the breadth and scope of the present invention shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims appendedhereto and their equivalents.

1. Lighting unit for vehicles comprising: a plurality of semiconductorlight sources (3) distributed in a grid, the grid of semiconductor lightsources being divided into at least two grid segments, the grid segmentsbeing each activatable independently of each other; an optical element(2) in the beam path of a light beam emitted by the semiconductor lightsources, the semiconductor light sources (3) being arranged on a commoncarrier substrate (5), with a chip cover (6) transparent to light in thedirection of light propagation, the chip cover (6) is filled with alight-scattering or light-converting auxiliary material (8); and ashading device (9), in the boundary region between one of said gridsegment (10) and another of said grid segment (11), such said shadingdevice increases a gradient of light intensity at a light/dark boundary.2. Lighting unit according to claim 1, wherein the shading device (9) isarranged in the boundary region between an activated grid segment (10)and an unactivated grid segment (11).
 3. Lighting unit according toclaim 1 wherein the shading device (9) is designed as a partition whichseparates the two grid segments (10, 11) from each other and whichprojects from the carrier substrate (5) in the direction of lightpropagation.
 4. Lighting unit according to claim 3, wherein the shadingdevice extends perpendicularly to the carrier substrate (5) and in thatthe free end of the shading device is arranged at a distance from and/ortapering towards a front side (15) of the chip cover (6).
 5. Lightingunit according to any of claim 1 wherein the semiconductor light sources(3) of the at least two grid segments (10, 11) are designed as aplurality of chips emitting UV radiation and/or emitting blue light, andarranged in the form of a semiconductor light source array.
 6. Lightingunit according to claim 5, wherein the semiconductor light source (3)array is arranged in a focal plane of the optical element (2, 16). 7.Lighting unit according to any of claim 1 wherein the shading device hasa longitudinal extent in the direction of the path of the carriersubstrate (5) corresponding to the formation of the light/dark boundary.8. Lighting unit according to any of claim 1 wherein the auxiliarymaterial (8) is formed as a light converter, in particular by aluminescent material.
 9. Lighting unit according to any of claim 1wherein the carrier substrate (5) is of flat or curved construction. 10.Lighting unit according to any of claim 1 wherein on a front side (15)of the chip cover (6) facing away from the carrier substrate (5) isarranged an optical element (16) resting directly on the chip cover (6).11. The lighting unit of claim 1 wherein said common carrier substrateis substantially on a single plane.
 12. The lighting unit of claim 1wherein said steeper transition of light intensity is formed in alight/dark boundary between said first grid segment and said second gridsegment.
 13. The lighting unit of claim 1 wherein said shading device iscompletely surrounded by said chip cover and contiguous with said chipcover.
 14. The lighting unit of claim 1 wherein said chip cover is aplanar cast body adjoining said common carrier substrate.
 15. Thelighting unit of claim 1 wherein said shading device is fixedly attachedto said common carrier substrate.
 16. The lighting unit of claim 1wherein said shading device is between said common carrier substrate andany optical element relative to a direction of light propagation. 17.The lighting unit of claim 1 wherein said optical element abuts saidchip cover, said chip cover abuts said light sources and said commoncarrier substrates.
 18. The lighting unit of claim 1 wherein said commoncarrier substrate is a single substrate.
 19. The lighting unit of claim1 wherein said shading device reduces an edge stripe when only one ofsaid grid segments is illuminated.
 20. The lighting unit of claim 1wherein said shading device increases light separation between said twogrid segments.